/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_MEMORY_REGION_H_
#define ART_RUNTIME_MEMORY_REGION_H_
#include <stdint.h>
#include <type_traits>
#include <android-base/logging.h>
#include "arch/instruction_set.h"
#include "base/bit_utils.h"
#include "base/casts.h"
#include "base/macros.h"
#include "base/value_object.h"
#include "globals.h"
namespace art {
// Memory regions are useful for accessing memory with bounds check in
// debug mode. They can be safely passed by value and do not assume ownership
// of the region.
class MemoryRegion FINAL : public ValueObject {
public:
struct ContentEquals {
constexpr bool operator()(const MemoryRegion& lhs, const MemoryRegion& rhs) const {
return lhs.size() == rhs.size() && memcmp(lhs.begin(), rhs.begin(), lhs.size()) == 0;
}
};
MemoryRegion() : pointer_(nullptr), size_(0) {}
MemoryRegion(void* pointer_in, uintptr_t size_in) : pointer_(pointer_in), size_(size_in) {}
void* pointer() const { return pointer_; }
size_t size() const { return size_; }
size_t size_in_bits() const { return size_ * kBitsPerByte; }
static size_t pointer_offset() {
return OFFSETOF_MEMBER(MemoryRegion, pointer_);
}
uint8_t* begin() const { return reinterpret_cast<uint8_t*>(pointer_); }
uint8_t* end() const { return begin() + size_; }
// Load value of type `T` at `offset`. The memory address corresponding
// to `offset` should be word-aligned (on ARM, this is a requirement).
template<typename T>
ALWAYS_INLINE T Load(uintptr_t offset) const {
T* address = ComputeInternalPointer<T>(offset);
DCHECK(IsWordAligned(address));
return *address;
}
// Store `value` (of type `T`) at `offset`. The memory address
// corresponding to `offset` should be word-aligned (on ARM, this is
// a requirement).
template<typename T>
ALWAYS_INLINE void Store(uintptr_t offset, T value) const {
T* address = ComputeInternalPointer<T>(offset);
DCHECK(IsWordAligned(address));
*address = value;
}
// Load value of type `T` at `offset`. The memory address corresponding
// to `offset` does not need to be word-aligned.
template<typename T>
ALWAYS_INLINE T LoadUnaligned(uintptr_t offset) const {
// Equivalent unsigned integer type corresponding to T.
typedef typename std::make_unsigned<T>::type U;
U equivalent_unsigned_integer_value = 0;
// Read the value byte by byte in a little-endian fashion.
for (size_t i = 0; i < sizeof(U); ++i) {
equivalent_unsigned_integer_value +=
*ComputeInternalPointer<uint8_t>(offset + i) << (i * kBitsPerByte);
}
return bit_cast<T, U>(equivalent_unsigned_integer_value);
}
// Store `value` (of type `T`) at `offset`. The memory address
// corresponding to `offset` does not need to be word-aligned.
template<typename T>
ALWAYS_INLINE void StoreUnaligned(uintptr_t offset, T value) const {
// Equivalent unsigned integer type corresponding to T.
typedef typename std::make_unsigned<T>::type U;
U equivalent_unsigned_integer_value = bit_cast<U, T>(value);
// Write the value byte by byte in a little-endian fashion.
for (size_t i = 0; i < sizeof(U); ++i) {
*ComputeInternalPointer<uint8_t>(offset + i) =
(equivalent_unsigned_integer_value >> (i * kBitsPerByte)) & 0xFF;
}
}
template<typename T>
ALWAYS_INLINE T* PointerTo(uintptr_t offset) const {
return ComputeInternalPointer<T>(offset);
}
// Load a single bit in the region. The bit at offset 0 is the least
// significant bit in the first byte.
ALWAYS_INLINE bool LoadBit(uintptr_t bit_offset) const {
uint8_t bit_mask;
uint8_t byte = *ComputeBitPointer(bit_offset, &bit_mask);
return byte & bit_mask;
}
ALWAYS_INLINE void StoreBit(uintptr_t bit_offset, bool value) const {
uint8_t bit_mask;
uint8_t* byte = ComputeBitPointer(bit_offset, &bit_mask);
if (value) {
*byte |= bit_mask;
} else {
*byte &= ~bit_mask;
}
}
// Load `length` bits from the region starting at bit offset `bit_offset`.
// The bit at the smallest offset is the least significant bit in the
// loaded value. `length` must not be larger than the number of bits
// contained in the return value (32).
ALWAYS_INLINE uint32_t LoadBits(uintptr_t bit_offset, size_t length) const {
DCHECK_LE(length, BitSizeOf<uint32_t>());
DCHECK_LE(bit_offset + length, size_in_bits());
if (UNLIKELY(length == 0)) {
// Do not touch any memory if the range is empty.
return 0;
}
const uint8_t* address = begin() + bit_offset / kBitsPerByte;
const uint32_t shift = bit_offset & (kBitsPerByte - 1);
// Load the value (reading only the strictly needed bytes).
const uint32_t load_bit_count = shift + length;
uint32_t value = address[0] >> shift;
if (load_bit_count > 8) {
value |= static_cast<uint32_t>(address[1]) << (8 - shift);
if (load_bit_count > 16) {
value |= static_cast<uint32_t>(address[2]) << (16 - shift);
if (load_bit_count > 24) {
value |= static_cast<uint32_t>(address[3]) << (24 - shift);
if (load_bit_count > 32) {
value |= static_cast<uint32_t>(address[4]) << (32 - shift);
}
}
}
}
// Clear unwanted most significant bits.
uint32_t clear_bit_count = BitSizeOf(value) - length;
value = (value << clear_bit_count) >> clear_bit_count;
for (size_t i = 0; i < length; ++i) {
DCHECK_EQ((value >> i) & 1, LoadBit(bit_offset + i));
}
return value;
}
// Store `value` on `length` bits in the region starting at bit offset
// `bit_offset`. The bit at the smallest offset is the least significant
// bit of the stored `value`. `value` must not be larger than `length`
// bits.
void StoreBits(uintptr_t bit_offset, uint32_t value, size_t length);
void CopyFrom(size_t offset, const MemoryRegion& from) const;
template<class Vector>
void CopyFromVector(size_t offset, Vector& vector) const {
if (!vector.empty()) {
CopyFrom(offset, MemoryRegion(vector.data(), vector.size()));
}
}
// Compute a sub memory region based on an existing one.
ALWAYS_INLINE MemoryRegion Subregion(uintptr_t offset, uintptr_t size_in) const {
CHECK_GE(this->size(), size_in);
CHECK_LE(offset, this->size() - size_in);
return MemoryRegion(reinterpret_cast<void*>(begin() + offset), size_in);
}
// Compute an extended memory region based on an existing one.
ALWAYS_INLINE void Extend(const MemoryRegion& region, uintptr_t extra) {
pointer_ = region.pointer();
size_ = (region.size() + extra);
}
private:
template<typename T>
ALWAYS_INLINE T* ComputeInternalPointer(size_t offset) const {
CHECK_GE(size(), sizeof(T));
CHECK_LE(offset, size() - sizeof(T));
return reinterpret_cast<T*>(begin() + offset);
}
// Locate the bit with the given offset. Returns a pointer to the byte
// containing the bit, and sets bit_mask to the bit within that byte.
ALWAYS_INLINE uint8_t* ComputeBitPointer(uintptr_t bit_offset, uint8_t* bit_mask) const {
uintptr_t bit_remainder = (bit_offset & (kBitsPerByte - 1));
*bit_mask = (1U << bit_remainder);
uintptr_t byte_offset = (bit_offset >> kBitsPerByteLog2);
return ComputeInternalPointer<uint8_t>(byte_offset);
}
// Is `address` aligned on a machine word?
template<typename T> static constexpr bool IsWordAligned(const T* address) {
// Word alignment in bytes.
size_t kWordAlignment = static_cast<size_t>(GetInstructionSetPointerSize(kRuntimeISA));
return IsAlignedParam(address, kWordAlignment);
}
void* pointer_;
size_t size_;
};
} // namespace art
#endif // ART_RUNTIME_MEMORY_REGION_H_